A Spanish , Mexican and American co-production, it was filmed in Spain , directed by Brian Trenchard-Smith . A Spanish, Mexican and American co-production, it was filmed in Spain, directed by Brian Trenchard-Smith. Treasure hunters from around the world race to Mexico after a Middle Eastern luxury yacht explodes, sending a Shah's fortune and mysterious document to the bottom of the ocean. It starred Chuck Connors , Susana Dosamantes , Glenn Ford , Richard Roundtree and Henry Silva . Day of the Assassins book. Day of the Assassin is a 1979 action film. Day of the Assassin is a 1979 action film. Read 30 reviews from the world's largest community for readers. Day of the Assassin Not Rated | 1h 34min | Action , Drama | 25 December 1981 (Mexico) Treasure hunters from around the world race to Mexico after a Middle Eastern luxury yacht explodes, sending a Shah's fortune and mysterious document to the bottom of the ocean. It starred Chuck Connors, Susana Dosamantes, Glenn Ford, Richard Roundtree and Henry Silva.